Tuberoinfundibular dopamine is the predominant inhibitor of prolactin secreting lactotrophs within the anterior pituitary. Reproductive experience decreases both circulating prolactin levels and dopamine antagonist stimulated prolactin release. This dampening of prolactin secretion following birth and lactation may be the result of long-term changes in the tuberoinfundibular dopamine system or in the dopamine receptors on the cell surface of the lactotrophs. The goals of the proposed studies are to examine the effect of reproductive experience on dopamine release within the median eminance as well as the effect on postsynaptic dopamine receptors. In addition, I will examine the effect of reproductive experience on oxytocin, another central inhibitor of prolactin release, both with regard to oxytocinergic mediation of dopamine release as well as the ability of oxytocin to decrease prolactin release. Finally, I will examine the effect of reproductive experience of dopamine-mediated motoric and maternal behavior. Together these studies should elucidate whether the observed long-term changes in prolactin secretion are due to alterations in the tuberoinfundibular DA system and whether such changes are influenced by central oxytocin. Furthermore, these studies will address the possibility of prior parity influencing behavioral responses to dopaminergic drugs.